Intramedullary stabilization screw

Abstract

A bone screw for intramedullary fixation of hand or foot bones comprises three sections of a threaded distal portion, a threaded center portion and a threaded proximal portion. The threaded distal portion comprises a first full thread with a first constant diameter and a first constant pitch throughout the threaded distal portion, wherein an open end of the threaded distal portion forms a leading end of the bone screw. The threaded center portion comprises a second full thread with a second constant diameter and a second constant pitch throughout the threaded center portion, wherein the second constant diameter is the same as the first constant diameter, and the second constant pitch is smaller than the first constant pitch. The threaded proximal portion comprises a third full thread with a third constant diameter and a third constant pitch throughout the threaded proximal portion.

What is claimed is: 
     
       1. A bone screw for intramedullary fixation of hand or foot bones, comprising:
 a threaded distal portion including a first thread, the threaded distal portion having a first constant outer thread diameter and a first constant pitch throughout the threaded distal portion, wherein an open end of the threaded distal portion forms a leading end of the bone screw; 
 a threaded center portion including the first thread and a second thread, the threaded center portion having a second constant outer thread diameter and a second constant pitch throughout the threaded center portion, wherein the second constant outer thread diameter is the same as the first constant outer thread diameter, and the second constant pitch is smaller than the first constant pitch; and 
 a threaded proximal portion including the first thread, the threaded proximal portion having the first constant outer thread diameter and the first constant pitch throughout the threaded proximal portion, wherein an open end of the threaded proximal portion forms a driving end of the bone screw, and 
 wherein the first thread has the first constant outer thread diameter and the first constant pitch throughout the threaded distal portion, the threaded center portion, and the threaded proximal portion. 
 
     
     
       2. The bone screw of  claim 1 , wherein the bone screw is headless. 
     
     
       3. The bone screw of  claim 1 , wherein the threaded distal portion, the threaded center portion and the threaded proximal portion are fully threaded. 
     
     
       4. The bone screw of  claim 1 , wherein the second constant pitch is one half of the first constant pitch. 
     
     
       5. The bone screw of  claim 1 , wherein the second constant pitch is one third of the first constant pitch. 
     
     
       6. The bone screw of  claim 1 , wherein the threaded center portion of the bone screw includes at least six thread revolutions. 
     
     
       7. The bone screw of  claim 1 , wherein the threaded center portion of the bone screw includes at least eight thread revolutions. 
     
     
       8. The bone screw of  claim 1 , wherein the threaded center portion of the bone screw includes at least ten thread revolutions. 
     
     
       9. The bone screw of  claim 1 , wherein each of the threaded distal portion and the threaded proximal portion of the bone screw includes at least three thread revolutions. 
     
     
       10. The bone screw of  claim 1 , wherein at least part of the threaded distal portion of the bone screw is self-tapping. 
     
     
       11. The bone screw of  claim 1 , wherein the bone screw is configured for intramedullary fixation of metacarpals or metatarsals. 
     
     
       12. The bone screw of  claim 1 , wherein the first constant outer thread diameter of the bone screw is sized such that the first constant outer thread diameter of the bone screw fits within an intramedullary canal of a hand or foot bone. 
     
     
       13. The bone screw of  claim 12 , wherein the hand or foot bone is either a metacarpal or a metatarsal. 
     
     
       14. The bone screw of  claim 13 , wherein the threaded proximal portion and the threaded distal portion of the bone screw engage cancellous bones of either end of the metacarpal or the metatarsal, and the threaded center portion of the bone screw engages an isthmus, in the center of the metacarpal or the metatarsal. 
     
     
       15. The bone screw of  claim 1 , wherein the threaded center portion includes more than two threads. 
     
     
       16. A bone screw for a metacarpal or a metatarsal, comprising:
 a threaded distal portion configured and adapted for insertion into an intramedullary canal of a first bone section of the metacarpal or the metatarsal; 
 a threaded center portion configured and adapted for insertion into the intramedullary canal of a second bone section of the metacarpal or the metatarsal; and 
 a threaded proximal portion configured and adapted for insertion into the intramedullary canal of a third bone section of the metacarpal or the metatarsal, 
 wherein each of the threaded distal portion and the threaded proximal portion has a first constant outer thread diameter and a first constant pitch, 
 wherein the threaded center portion has a second constant outer thread diameter and a second constant pitch throughout the threaded center portion, and 
 wherein the second constant outer thread diameter is the same as the first constant outer thread diameter, and the second constant pitch is smaller than the first constant pitch. 
 
     
     
       17. The bone screw of  claim 16 , wherein the first bone section and the third bone section are cancellous bone sections of the metacarpal or the metatarsal. 
     
     
       18. The bone screw of  claim 16 , wherein the second bone section is an isthmus bone section of the metacarpal or the metatarsal.